This invention relates to a magnetic disk cartridge in which a disk-shaped magnetic recording medium which is extremely thin, namely, a magnetic disk sheet, is rotatably supported. More particularly, the invention relates to a magnetic disk cartridge in which the sheet surface cleaning means is improved.
2. Background Art
As is well known, a floppy disk has been proposed in the art. The floppy disk is made by forming magnetic layers on both sides of a disk-shaped substrate which is made of flexible polyester sheet. Signals are magnetically recorded on the magnetic layers with a magnetic head while the floppy disk is being rotated. As the floppy disk can be readily handled and is low in manufacturing cost, it is extensively employed as a recording medium for computers.
On the other hand, a so-called "micro floppy disk" has been put in practical use. The micro floppy disk utilizes the above-described advantages of the floppy disk and the advantage of the magnetic recording operation in which the recording medium, unlike a silver salt film, can be repeatedly used. The micro floppy disk is made smaller in size than the floppy disk so that it can be more readily handled.
In general, in magnetically writing data in the above-described magnetic disk sheet or reading them from the disk sheet, the writing head or reading head is slidably moved radially of the magnetic disk sheet (in practice, the head being moved in a contactless mode). Accordingly, if, in the data writing or reading operation, the magnetic head is unsatisfactorily confronted with the magnetic disk sheet or dust enters beneath the head gap, then the signal inputting or outputting operation is made irregular, thus causing dropouts. In a 3.5 inch magnetic disk cartridge, in order to improve its reliability, the case is made of relatively hard material, and the opening through which the magnetic head is brought into contact with the magnetic disk sheet is provided with a dust-proof shutter. Furthermore, liners of rayon or polyester unwoven cloth are interposed between the magnetic disk sheet and the case inner walls in such a manner that the liners are slightly pushed against the recording surfaces of the magnetic disk sheet so that dust or small particles are removed from the disk sheet while the sheet is being rotated. In addition, a lifter of polyethylene terephthalate (PET) is disposed between the case inner wall and the liner. The lifter is in the form of a rectangular sheet having one end portion fixedly secured to the case inner wall and the other end portion which rises obliquely in the case. Therefore, the liners are pushed against the surfaces of the magnetic disk sheet by the lifter.
However, the conventional lifter of PET resin soon relaxes. That is, it is impossible for the conventional lifter to stably push the magnetic disk sheet over a long period.
On the other hand, the lifter is secured with a double-sided adhesive tape or an instantaneous adhesive agent. However, the fixing method manifests considerably low productivity in the manufacture of the magnetic disk cartridge.